Organic Chemistry Flashcards
Paper 2 - C7
What is crude oil?
A mixture of molecules called hydrocarbons
Where do we find crude oil?
In rocks
Is crude oil a finite or infinite resource?
Finite
How is crude oil formed?
Crude oil is formed over millions of years from the remains of tiny sea creatures called plankton which were buried in mud.
What is a hydrocarbon?
Hydrocarbons are molecules made up of hydrogen and carbon atoms only.
What is an alkane?
A saturated hydrocarbon which have carbon atoms in chains linked by single bonds.
What is the general formula of an Alkane?
CnH₂n+₂
What are the first four alkanes?
Methane (smallest)
Ethane
Propane
Butane (largest)
What does viscosity tell us?
Tells us the thickness of a fluid
What happens if the size of the hydrocarbons increases in terms of viscosity?
As the size of the hydrocarbon molecules increases, the molecules get more viscous.
What does flammability tell us?
Tells us how easily a hydrocarbon combusts (burns)
What happens if the size of the hydrocarbons increases in terms of flammability?
As the size of the hydrocarbon molecules increases, the molecules get less flammable.
What does the boiling point tell us?
Tells us the temperature at which a liquid turns into a gas
What happens if the size of the hydrocarbons increases in terms of boiling points?
As the size of the hydrocarbon molecules increases, the boiling point also increases.
How can hydrocarbons be used as fuel?
Hydrocarbon fuels release energy when combusted. During combustion the carbon and hydrogen atoms in the fuel react with oxygen. The carbon and hydrogen are oxidised.
What happens if the supply of oxygen is unlimited during combustion?
Water and carbon dioxide are produced
What process can we use to separate hydrocarbons?
Fractional distillation
Where does fractional distillation take place in?
Large columns
What are the stages of fractional distillation?
-Firstly, the crude oil is heated to a very high temperature. This causes the crude oil to boil.
-The crude oil vapour is now fed into the fractional distillation column and the column is hotter at the bottom and cooler at the top.
-The hydrocarbon vapours now rise up the column and the hydrocarbons condense when they reach their boiling point.
-The liquid fractions are then removed.
-The remaining hydrocarbons continue moving up the column and these now condense when they reach their boiling points.
What do fractions contain in fractional distillation?
In fractional distillation crude oil is separated into fraction. Fractions contain hydrocarbons with a similar number of carbon atoms.
Where do very long chain hydrocarbons get removed from in fractional distillation?
At the bottom of the column because of their high boiling points.
Where do very short chain hydrocarbons get removed from in fractional distillation?
At the top of the column because of their low boiling points and they do not condense and they get removed as gases.
What types of fuel are fractions used as?
-Petrol and diesel
-Kerosene
-Heavy fuel oil
-Liquified petroleum gas
What is it meant by feedstock?
A chemical that is used to make other chemicals.
What types of feedstock are fractions used as?
-Solvents
-Lubricants
-Detergents
-Polymers
What is it meant by cracking?
When a long-chain alkane is broken down (cracked) to produce smaller, more useful molecules.
What are the two ways we can carry out cracking?
Catalytic cracking
Steam cracking
What are the conditions for catalytic cracking?
-High temperature
-With a catalyst
What are the conditions for steam cracking?
-High temperature
-With steam
What is it meant by an alkene?
Unsaturated hydrocarbons with at least one carbon-to-carbon double bond.
Why are alkenes useful?
-They can be used to polymers.
-They are also used as a starting material for other useful chemicals as well.
-And they are more reactive than alkanes.
How do we test for an alkene?
By using bromine water if we shake our alkene with bromine water then the bromine water will turn colourless.